| Sys.getenv_value | R Documentation | 
System Environment Variables
Sys.getenv_value(name, raw = FALSE)
| name | variable name as a character string. | 
| raw | logical that indicates if one should return the raw value or
the convertion of any false value to  | 
the value of the environment variable as a character string or
NA is the variable is not defined at all.
# undefined returns FALSE
Sys.getenv_value('TOTO')
# raw undefined returns NA
Sys.getenv_value('TOTO', raw = TRUE)
Sys.setenv(TOTO='bla')
Sys.getenv_value('TOTO')
# anything false-like returns FALSE
Sys.setenv(TOTO='false'); Sys.getenv_value('TOTO')
Sys.setenv(TOTO='0'); Sys.getenv_value('TOTO')
# cleanup
Sys.unsetenv('TOTO')
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